1. Field of Invention
The present invention relates to a method and an apparatus for controlling the density of products and, more particularly, to products produced from a foam extrusion process.
2. Prior Art
In a foam extrusion system, materials such as resin, additives, and blowing agent are all introduced into an extruder. The resin and additives are heated (e.g., 450.degree. F. or 230.degree. C.) and are mixed with the blowing agent to form a mixture. The mixture is then cooled and is extruded through a die. Products produced from such a foam extrusion system include disposable cups and dishes, egg cartons, and meat trays.
In certain applications, it is highly desirable to control the density of the products produced by such a foam extrusion system. Heretofore, however, such control has been formed manually, and has been lacking in accuracy and speed of response.